The present embodiment relates generally to a sealing composition for sealing a subterranean zone penetrated by a well bore.
In the drilling and completion of an oil or gas well, a cementing composition is often introduced in the well bore for cementing pipe string or casing. In this process, known as “primary cementing,” the cementing composition is pumped into the annular space between the walls of the well bore and the casing. The cementing composition sets in the annular space, supporting and positioning the casing, and forming a substantially impermeable barrier, or cement sheath, which isolates the well bore into subterranean zones. Thus, the undesirable migration of fluids between zones is prevented after primary cementing.
Changes in pressure or temperature in the well bore over the life of the well can result in compromised zonal isolation. Also, activities undertaken in the well bore, such as pressure testing, well completion operations, hydraulic fracturing, and hydrocarbon production can affect zonal isolation. Such compromised zonal isolation is often evident as cracking or plastic deformation in the cementing composition, or de-bonding between the cementing composition and either the well bore or the casing. Compromised zonal isolation requires remedial operations to reestablish isolation between the zones.
One such remedial operation is known as a squeeze, where pressure is used to force a sealing composition into cracks or other leak paths and restore zonal isolation. Accordingly, a sealing composition comprising cement can be used in a squeeze operation to plug a perforated interval of casing and sheath, and is particularly useful for such a use because cement allows subsequent re-perforation if desired. Therefore, a sealing composition incorporating cement, but having superior sealing properties, is desirable for squeeze operations.